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wolrah posted:Another "why the hell do they do this?" post: Sounds like a bad use of the sign.. does the intersection ever get really crowded? There's an intersection near me that restricts right turns on red during peak hours so right turners don't trap through motorists in the intersection and block everyone else. Call the transportation department and ask. MUTCD posted:Guidance: Longpig Bard fucked around with this message at 06:22 on Jun 29, 2010 |
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Jun 29, 2010 05:53
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Bumming Your Scene posted:Sounds like a bad use of the sign.. does the intersection ever get really crowded? There's an intersection near me that restricts right turns on red during peak hours so right turners don't trap through motorists in the intersection and block everyone else. Unfortunately, some jurisdictions just stick NTOR up like candy. For a time, our policy was to post NTOR at every signal. Also note that the MUTCD says "should," which is the same as "shall" in some states, but the rest of us tend to ignore guidance statements when we find it convenient. Heck, we even ignore standards once in a while.
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Jun 29, 2010 17:12
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I noticed this past week that there were traffic counters (correct term?) set up at various points on Route 2. From what I noticed, they were at the ramps of exit 21, then slightly east of exit 22, now they are on the ramps of exit 27. What is done with the info that is gathered?
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Jul 1, 2010 11:26
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porkfriedrice posted:I noticed this past week that there were traffic counters (correct term?) set up at various points on Route 2. From what I noticed, they were at the ramps of exit 21, then slightly east of exit 22, now they are on the ramps of exit 27. What is done with the info that is gathered? Summer is the best time to do daily counts, since volumes are highest and the pneumatic tubes won't get plowed up. Typically, the technicians will do one town a day, placing the counters across each ramp at ~5 a.m. and taking them out around 6 the next morning. With at least 24 hours of data, we can add or subtract those ramps from the hourly counts done at the nearest continuous count station on the freeway (the loops you see in the pavement). In this very tedious way, we can obtain relatively accurate hourly counts for just about any spot on the freeway. Of course, if your project is far enough away from a continuous count station, little errors will begin to accumulate when you add/subtract ramp volumes. Since not every ramp is done on the same day, and there are sometimes accidents, the measured daily volume on each ramp can be several percent off of the true AADT. Add all those little errors up, and your freeway volumes can get really messed up. I once added/subtracted ramp volumes on 395 from the Norwich CCS to the Killingly CCS, just to calibrate it, and the volumes were at least 10 percent off. The easier, and sometimes more accurate, way to do things is to just take those hourly counts at the CCS and multiply them by the ratio of the ADT at your project to the ADT at the CCS. The farther away your project from the count station, the less accurate your hourly volumes, but the directional split and total ADT should be spot-on.
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Jul 1, 2010 12:37
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For anyone who's wondered what traffic engineering was like before computers, here's a 40-year-old handbook that uses nomographs to calculate queue lengths, signal capacity, cycle lengths, and the like. Have a look!    Nomographs are pretty great, because all you need to do them is a pencil and a straightedge. Unfortunately, their complexity and apparent precision hides the fact that the equations upon which they're based are quite approximate and, in this case, probably out-of-date.
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Jul 1, 2010 22:08
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Cichlidae posted:Out of curiosity, why wouldn't you cut through the adjacent residential area on the right? The western entrance isn't signalized, and Secor Road north of its intersection with Dorr looks like it carries some heavy volumes, so the Secor Road phase should come in often. I actually hadn't thought about that way. I'll give it a shot next time I go through there since my route takes me up Secor to the highway.
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Jul 2, 2010 18:07
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A few miles after crossing the MA border into CT on I84WB there are a pair of sensors suspended over the highway. Are these for the weigh station just down the road or just a different type of traffic counting system other than loop detectors embedded in the highway?
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Jul 3, 2010 01:50
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Lobstaman posted:A few miles after crossing the MA border into CT on I84WB there are a pair of sensors suspended over the highway. I haven't seen those before, but that looks like weight-in-motion sensors in the pavement combined with vehicle height/length sensors in the air. It could be to warn overheight vehicles, or to indicate to officers manning the weigh station how many and what type of trucks are coming. I'd guess at the latter, because we haven't had much luck with overheight warnings in the past. I'll see if anyone else in Traffic knows about them.
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Jul 3, 2010 16:41
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Stolen from GBS, but everything about this link is awesome: http://www.youtube.com/watch?v=A1pHgp5Og08
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Jul 6, 2010 02:51
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Cichlidae posted:I haven't seen those before, but that looks like weight-in-motion sensors in the pavement combined with vehicle height/length sensors in the air. It could be to warn overheight vehicles, or to indicate to officers manning the weigh station how many and what type of trucks are coming. I'd guess at the latter, because we haven't had much luck with overheight warnings in the past. I'll see if anyone else in Traffic knows about them. Yeah, they are most likely WIM/AVI (automatic vehicle identification) sensors. I see them all the time before weigh stations in Illinois. Trucks that pass the WIM can skip the weigh station which helps with the efficiency and safety of the weight stations.
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Jul 6, 2010 04:41
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EoRaptor posted:Stolen from GBS, but everything about this link is awesome: Very cool. In a similar vein, here's the Providence River Bridge, which was floated a few miles up the Bay and set down on its piers with the receding tide: http://www.youtube.com/watch?v=vROwFWDNe1c TMMadman posted:Yeah, they are most likely WIM/AVI (automatic vehicle identification) sensors. I see them all the time before weigh stations in Illinois. Fifteen years ago, ITS was just a buzzword you quoted to make your boss feel behind the times. These days, it's starting to come together 
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Jul 6, 2010 12:35
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Cichlidae posted:Fifteen years ago, ITS was just a buzzword you quoted to make your boss feel behind the times. These days, it's starting to come together Yeah. I love the I-Pass system in Illinois (compatible with the E-ZPass of the Northeast) and it generally makes for much smoother commutes. Of course it is almost required to get the I-Pass now if you do any driving on the Illinois tollways because not having an I-Pass means you have to pay double the toll.
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Jul 6, 2010 16:45
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TMMadman posted:Yeah. I love the I-Pass system in Illinois (compatible with the E-ZPass of the Northeast) and it generally makes for much smoother commutes. Of course it is almost required to get the I-Pass now if you do any driving on the Illinois tollways because not having an I-Pass means you have to pay double the toll. Wow, thats quite the discount/penalty. The discount in NY is about 5-10% percent. Do they charge any kind of membership fees? I don't use my EZ pass as much as I used to, but I keep it because there is no downside.
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Jul 6, 2010 20:24
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To Porkfriedrice: They are indeed truck sensors, to detect RFID tags on the trucks so they won't have to stop at the weigh station. There is also a Geiger counter to detect any potential dirty bombs sneaking their way to NYC  Guy Axlerod posted:Wow, thats quite the discount/penalty. The discount in NY is about 5-10% percent. The Newport Bridge toll's a pretty extreme example of disparity, though it's by origin, not payment method. Rhode Island E-Zpass users pay $0.83/crossing, while out-of-staters in either cash or E-Zpass pay $4.00.
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Jul 6, 2010 21:45
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Cichlidae posted:To Porkfriedrice: They are indeed truck sensors, to detect RFID tags on the trucks so they won't have to stop at the weigh station. There is also a Geiger counter to detect any potential dirty bombs sneaking their way to NYC
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Jul 6, 2010 22:34
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porkfriedrice posted:I think you meant Lobstaman, but that's okay! By the way, did you ever find out any info about those doors in the bridge abutments? (Maybe it's top secret and you "forgot") Still haven't seen any Bridge guys hanging around. One's my golf partner, so I'll see him on Thursday and ask. He's been rather busy with that Route 67 bridge collapse lately, so we have plenty to talk about.
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Jul 6, 2010 22:40
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EoRaptor posted:Stolen from GBS, but everything about this link is awesome:
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Jul 8, 2010 16:49
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smackfu posted:That's pretty crazy. What puzzles me is that I thought building the piers and stuff in the water was the hard part of building a bridge, and this method would require doing that just for the temporary detour. If it's absolutely essential to maintain traffic flow while the bridge is replaced, whether because the volumes are too high or the next bridge is 20 miles away, the cost of building a temporary crossing is less than the user cost of a detour. Let's grab some rough numbers and say 20,000 people a day would have to be diverted, times a 20-mile trip (so about 20,000 gallons of gas/day, plus 10,000 man-hours of delay), plus additional congestion on the next bridge and approach roadways (let's call that another 3,000 man-hours of delay and 3,000 gallons of gas). That's 23,000 gallons of gas, about $70k, and 13,000 man-hours, about $130k, wasted every single day. In just five days, you've lost a million dollars. If building that temporary bridge would cost $20 million, and your project is going to last 8 months, why not? (I know the Red Book recommends lower numbers for user costs, but that's old, and I didn't factor in environmental or accident costs and other stuff like that.)
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Jul 8, 2010 21:49
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I just heard about this the other day: http://www.autoblog.com/2010/07/03/report-many-detroit-area-speed-limits-are-set-at-illegally-lo/ quote:It's probably a safe bet that many Autoblog readers find speed limits very annoying in general. To that end, it turns out that a significant number of limits in Michigan may, in fact, be illegal. Researchers have known for years that when it comes to safety, speed limits should be set at the 85th percentile traffic flow speed. The reality is that most drivers move along at what they consider to be a safe speed for the conditions regardless of the posted limit. To minimize accidents, the limit should therefore be the speed at which 85 percent of the drivers are moving. Good news for me, since I'm pretty sure a road I drive every day is limited well below the 85th.
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Jul 9, 2010 04:15
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This may be a dumb question, or you guys may have already talked about it, but is there any reason the reflective paint they use on roads is so slick? Mostly in the rain, obviously, but even when its dry.
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Jul 9, 2010 04:20
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Zero One posted:I just heard about this the other day: Yep, I've done plenty of speed surveys to know immediately when I'm driving on a road with an unreasonably low speed limit. Doesn't have to do with increasing ticket revenues, law enforcement and road departments aren't in cahoots. It has to do with lack of manpower to get out and update the speed limit or city council/board of supervisors bullying the engineer. I can't really speak for smaller cities though. Longpig Bard fucked around with this message at 05:16 on Jul 9, 2010 |
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Jul 9, 2010 04:47
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Zero One posted:I just heard about this the other day: Boy, that's a great law. The latest MUTCD makes an even stronger point that the speed limit is based on the 85th %ile speed, so there's really no excuse anymore. Bumming Your Scene posted:Yep, I've done plenty of speed surveys to know immediately when I'm driving on a road with an unreasonably low speed limit. Manpower isn't a big hurdle if you have a little motivation. All it takes is one guy with a half hour free and a speed gun, and you can get a very good approximation. Even if they really can't afford it, the state does traffic counts once every three years on town roads with significant volume, and it's only a matter of sticking one more tube on the ground to get a speed survey out of that. Like you said, towns bullying the engineer and ESPECIALLY citizen complaints is the main reason speed limits get pushed down. If the police were worried about their revenue, it's still a $75 ticket for driving 1 mph over the limit; they'd just start enforcing closer to the posted speed. blugu64 posted:This may be a dumb question, or you guys may have already talked about it, but is there any reason the reflective paint they use on roads is so slick? Mostly in the rain, obviously, but even when its dry. Well, first off, there are three kinds of pavement markings. The vast majority of states use paint, some just spraying it onto the pavement with no additional treatment. A few, Connecticut included, use epoxy resin. Even fewer use thermoplastic. The markings include a liberal scattering of glass beads to make them retroreflective. Epoxy and thermoplastic in particular can get slippery, because they are put down in thicker layers and can mask the texture of the road. Those glass beads help somewhat, especially when the marking is brand new. As time goes by, though, they get rubbed away and the marking is worn down, exposing the bead-less layers beneath. This smooth layer isn't very good at providing traction. It's not an intentional effect, it's just an unfortunate result of how pavement markings are made.
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Jul 9, 2010 12:41
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Hey Cichlidae, I had a random thought from a coworker and I wanted to hear what you feelings on the subject. Here in Washington (and everywhere else I'm sure) there are PSAs about the dangers of texting and talking on the phone while driving. Yet, I've never seen or heard one addressed at employers who expect their employees to be available on the phone at all times? Maybe the data doesn't pan out, but there are a lot of employees out there who are expected to answer the company phone right then and there and if they don't there's hell to pay. I wonder how many of those situations happen on the road and lead to accidents. What do you think?
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Jul 12, 2010 04:20
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There's some level of corporate liability if that is indeed the case, though. I have a company-paid phone (and thus am expected to be essentially on-call) but at our workplace, everyone in that category has to sign an agreement that includes not answering the phone while driving a car.
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Jul 12, 2010 05:04
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IOwnCalculus posted:There's some level of corporate liability if that is indeed the case, though. I have a company-paid phone (and thus am expected to be essentially on-call) but at our workplace, everyone in that category has to sign an agreement that includes not answering the phone while driving a car. It's a good point, though my experience is colored by the fact that bosses call people in on their personal cell phones. It's important to remember that not every business is run by someone willing to legally protect themselves. Even then, there's still the unspoken expectation that you will pick up that phone right when the boss wants you too, and not a moment after.
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Jul 12, 2010 06:21
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IOwnCalculus posted:There's some level of corporate liability if that is indeed the case, though. I have a company-paid phone (and thus am expected to be essentially on-call) but at our workplace, everyone in that category has to sign an agreement that includes not answering the phone while driving a car.
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Jul 12, 2010 10:46
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If it were a company phone, I suppose it would depend on the company's official policy. I imagine most have a rule on the books (I know mine does) that talking on the phone while driving is forbidden. However, in the private sector, I wouldn't be surprised if that's followed up with a verbal agreement to answer it anyway, and not doing so could hurt someone's career advancement. When you crash, your boss just cites company policy and says, "I didn't know he was in the car when I called. Honest!" If it were a personal phone, there's a pretty solid reason for not using it for business. If your boss wants to call you when you're on the road, and can't wait for you to get home to tell you something, then you should have a company phone. If you get into an accident while on a personal phone, it doesn't matter who's calling; you're at fault. I turn my phone off when I'm driving, and when I'm at work, unless I'm out in the field. If I'm not at work, I'm not going to get a call, anyway. There's nothing so important that it can't wait until the next morning. Isn't being a public sector employee great?
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Jul 12, 2010 12:51
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For an actual call, you can always use some kind of hands-free headset, which I think are considered acceptable for road safety.
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Jul 12, 2010 14:12
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Cichlidae posted:If it were a company phone, I suppose it would depend on the company's official policy. I imagine most have a rule on the books (I know mine does) that talking on the phone while driving is forbidden. However, in the private sector, I wouldn't be surprised if that's followed up with a verbal agreement to answer it anyway, and not doing so could hurt someone's career advancement. When you crash, your boss just cites company policy and says, "I didn't know he was in the car when I called. Honest!" I won't take this derail much further unless there is a specific desire to discuss traffic safety and public policy here. Anyway, this is the exact issue. There are many bosses out there who see the economy as an excuse to take certain liberties with their employees. The employee who won't take calls while on the road quickly becomes the employee who is calling the unemployment office instead.
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Jul 12, 2010 14:42
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smackfu posted:For an actual call, you can always use some kind of hands-free headset, which I think are considered acceptable for road safety. They're not. They produce the same degradation in driver ability as a handheld cell phone or alcohol.
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Jul 12, 2010 15:34
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Crackpipe posted:They're not. They produce the same degradation in driver ability as a handheld cell phone or alcohol. But still legal, unfortunately. Until last month, if you got caught for driving and talking on the phone in CT, you could even get the ticket waived if you bought a hands-free kit afterward.
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Jul 12, 2010 21:56
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Amazing thread! As an engineer (not traffic), this kind of stuff fascinates me. Onto my question! How sensitive are traffic light sensors? It seems that whenever I'm stopped behind a bicyclist while he is sitting on the left-turn lane sensor, we never get the green arrow, or it at least seems to take forever. Are these lane sensors designed to be sensitive enough for Lance rear end in a top hat Armstrong to be detected? Apologies if this has been asked already. I have about 45 pages to get caught up on!
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Jul 14, 2010 00:52
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crumshot posted:Amazing thread! As an engineer (not traffic), this kind of stuff fascinates me. The inductive loop detectors in the pavement are tuned to recognize cars and other giant chunks of conductive material. Their detection area rises like a bubble above the loop itself, detecting things up to ~3 feet in the air. However, the sensitivity in the middle of the loop is pretty low; it's strongest at the edges. The cheapest solution is a quadrupole loop, which looks more like a rectangular figure-eight. It's effectively two loops, each half the width of the original. The shared border of those two loops is extremely sensitive, and we can paint a line there to tell bikes to stop there and call the green. However, this sacrifices the height of the detection bubble, which is now more like 18". Taller trailers can pass over a quadrupole loop without triggering it. So, the next time you're stuck behind a bike and it's not triggering the loop, tell him to position his bike right on the edge. If that doesn't do it, the loop just isn't sensitive enough to detect a bicycle.
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Jul 14, 2010 02:31
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I know you are out on the east coast somewhere, but fix these interchanges in the Chicagoland area: I-55/I-294, I-294/I-290, the I-90/I-94 split/merge and while you're at it do something about the The Circle Interchange (wiki link) http://en.wikipedia.org/wiki/Circle_Interchange Seriously, all of the interchanges in the Chicagoland interstate system are completely hosed up. For example, I realized today that I couldn't go from northbound I-294 to westbound I-94, which I suppose makes a perverted kind of sense since technically I-294 ends at that point and becomes I-94, but it I was still irritated that I had to go to the next exit and get back on going the other way. edit - Also, we used to have the famous 'Hillside Strangler' merge: Named after the Chicago suburb of Hillside, it refers to a major merge with Interstate 88, and almost always is used when referring to inbound (eastbound) traffic. It is at this point that Interstate 88 terminates eastbound. It was called the Strangler because before its reconstruction in the early 2000s, seven through lanes were forced to merge to three, creating large backups. Urban legend suggests that the former Columbia College student Robert Spryszak was the first known to use the expression relating to the traffic pattern in the late 70s during the "Hillside Strangler" murders media craze. Reconstruction widened part of this area to nine lanes (five inbound; three through; two local; and four through lanes outbound). This allowed direct exits to Mannheim Road (U.S. Routes 12/20/45) from Interstate 88, the ramp also serving for an Interstate 88 truck access to eastbound Interstate 290; created an inbound collector-distributor ramp for Mannheim Road; and added a timed gate that closed a ramp from Roosevelt Road (Illinois Route 38) to inbound Interstate 290 during the afternoon rush hours. These improvements helped congestion at the site, but they also pushed pre-existing congestion further east to the six-lane portion of the highway. The Hillside Strangler is located at about mile marker 18. edit 2 - Also just to try and give you an aneurysm, take a look at this: http://maps.google.com/maps?hl=en&ie=UTF8&ll=41.987312,-87.854533&spn=0.02386,0.066047&t=k&z=15 edit 3 - added links to the interchanges TMMadman fucked around with this message at 04:20 on Jul 14, 2010 |
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Jul 14, 2010 04:05
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TMMadman posted:I know you are out on the east coast somewhere, but fix these interchanges in the Chicagoland area: I-55/I-294, I-294/I-290, the I-90/I-94 split/merge and while you're at it do something about the The Circle Interchange (wiki link) http://en.wikipedia.org/wiki/Circle_Interchange As someone who lives on the Eisenhower (I-290), I've learned that it's best to pretend the Eisenhower doesn't exist during rush hour. I used to commute from Oak Park to Schaumburg; the morning commute out was fine, but there was no point using the highway on the way home, other streets were much faster. There isn't much hope for I-290 because of how built up it is along the sides. The Oak Park congestion could be solved by rebuilding the intersections to replace left-hand exits with right-hand ones and adding lanes by turning the CTA Blue Line that runs alongside into a subway. As for the new Hillside Strangler, I don't know if anything can be done, the roadway is sunk between solid rows of private property. We may be stuck with that headache until car traffic is replaced by jetpacks or teleporters or something.
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Jul 14, 2010 05:15
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Kakairo posted:As someone who lives on the Eisenhower (I-290), I've learned that it's best to pretend the Eisenhower doesn't exist during rush hour. I used to commute from Oak Park to Schaumburg; the morning commute out was fine, but there was no point using the highway on the way home, other streets were much faster. Yeah, I tend to avoid the Ike at rush hour too and I know it can't really be fixed. Thankfully I have lived in the southwestern burbs for 37 years, so most of the time I have mostly been able to avoid the Ike and instead get to take the Stevenson into the city which usually isn't terrible during rush hour, just in patches. It just sucks for me right now since I am delivering stuff all over Chicagoland right now, so I am constantly on all the expressways but most of the time isn't during rush hours, but there are always problem spot and the never ending second Chicago season.
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Jul 14, 2010 08:46
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TMMadman posted:Chicago! Alright, let's have a crack at them. 1: I-55 & I-294: There's not much that can be done here, mostly because of the tolls. If you have toll booths, you're pretty much stuck with a quadrant interchange (or a partial one like you have here). Get rid of the tolls, and you still have some trouble, because there's no land available. The interchange itself isn't awful, just complex. 2: I-294/I-290: Put both freeways on the same stretch of pavement: I-294 as express lanes in the middle, I-290 as a wide collector-distributor road on the outside. Separate them by a narrow median with a barrier, and put a couple slip roads back and forth. This simplifies all of the interchanges, because now there's only one freeway, not two. Weaving would be a problem, but it's not too difficult to stick in ramps to the inner roadway (I-294) as shown in the picture. I turned the cloverleaf into a diamond because cloverleafs suck.  3: I-90/I-94 split: Hmm, that's not all too bad. You've got reversible lanes, which make things a bit more complex, and the ramps to/from Keeler Ave introduce weaving problems. Close those two ramps and the problem disappears. Depending on the volumes, it could be advantageous to add direct access between 90 EB --> 94 WB and 94 EB --> 90 WB. 4: The Circle Interchange: Simple enough. There's tons of weaving thanks to the excessive number of ramps on 90/94. Put a collector/distributor road in and consolidate ramps to fix it. Exits are supposed to be a mile apart, not every block. The interchange itself suffers from insufficient capacity. Make each ramp two lanes wide, three if needed, and build them as a directional stack instead of a turbine so they can carry more traffic at high speeds. It'll be much taller this way, but it's right near skyscrapers anyway.  5: Super turbo bonus round: Real engineers don't get aneurysms; we have heart attacks or commit suicide. 
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Jul 14, 2010 23:14
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Cichlidae posted:5: Super turbo bonus round: Real engineers don't get aneurysms; we have heart attacks or commit suicide. You always have such great ideas. But I can't imagine that every other traffic engineer is lacking, so why don't any of these fixes ever get done?
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Jul 15, 2010 02:38
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M_Gargantua posted:You always have such great ideas. But I can't imagine that every other traffic engineer is lacking, so why don't any of these fixes ever get done? Money, NIMBY, political tie-ups, endless red tape, incompetent contractors or consultants, and sometimes just too many engineers working in different directions. Good ideas are a good start, but there's always something that will hold them back if you let it.
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Jul 15, 2010 02:55
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Sorry if you have seen it before, but when I visited there this thing just blew me away... http://en.wikipedia.org/wiki/O-Bahn_Busway This thread has opened my eyes so much, I now notice the different styles of thinking employed where I live, based upon when an arterial road was constructed. If you have time I would like to show you some of the crazy stuff going on where I live, and get your opinion. Edit: Meant to say that this is an awsome thread. I am not your kind of engineer but I am currently working with the construction side of the major transport upgrades in the city I reside in, this makes some of the descisions we have to implement make sense! Moonboot fucked around with this message at 14:35 on Jul 19, 2010 |
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Jul 19, 2010 12:42
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